The growing threat of counterfeiting urgently requires the development of advanced optical security materials. Although fluorescence-based anti-counterfeiting technologies have certain advantages, traditional single-mode systems are still insufficient against complex counterfeiting methods. This study addresses this challenge by designing a lead-free double perovskite material that integrates multiple emission modes to enhance security. We synthesized Sb³⁺ and Er³⁺ co-doped Cs₂NaScCl₆ (CNSC) microcrystals via a hydrothermal method. The material exhibits dual-mode luminescence characteristics: (1) excitation wavelength-dependent down-conversion (DC) emission under ultraviolet (UV) light, enabling switchable blue-violet and blue-green outputs; (2) efficient up-conversion (UC) under near-infrared (NIR) excitation at 980 nm, 808 nm and 1532 nm. The Sb³⁺ dopant plays a dual role: it sensitizes the intrinsic blue self-trapped exciton (STE) emission and promotes the formation of metal-to-metal charge transfer (MMCT) states with Sc³⁺, enabling tunable STE-based luminescence. Er³⁺ doping introduces additional energy transfer pathways from STE states and allows NIR-to-visible UC luminescence through self-sensitization. The coexistence of excitation-dependent UV-responsive photoluminescence and multi-wavelength NIR-excited UC in a single material provides a higher level of security for optical encryption. This study demonstrates a promising strategy for developing complex multimodal anti-counterfeiting materials based on engineered lead-free double perovskites.

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) have Wide-ranging application prospects in fields such as night vision lighting, food detection, fluorescence labeling, and biological imaging. However, there is currently a lack of highly efficient phosphors covering the 700-1100 nm spectral range, and challenges remain in improving the efficiency and thermal stability. In this work, the Gd3Ga5O12: Cr3+ garnet phosphor was successfully synthesized, which exhibits good thermal stability (I180 degrees C/I30 degrees C = 93 %). When current was 10 mA, the fabricated pc-LED demonstrated an impressive photoelectric conversion efficiency reaching 28.11 %. After incorporating Yb3+, the emission wavelength range was broadened by 200 nm. The Gd3Ga5O12: Cr3+, Yb3+ phosphor achieved zero thermal quenching at 180 degrees C, and the corresponding pc-LED still maintained an excellent photoelectric efficiency of 25.86 % at 10 mA. The Gd3Ga5O12: 0.1Cr3+, 0.02 Yb3+ is an broad emission band, high conversion efficiency, and outstanding thermal stability NIR phosphor with high potential for compact highpower NIR pc-LEDs.

Noncontact optical temperature sensing enabled by intense upconversion luminescence (UCL) has attracted considerable attention. How to obtain luminescent materials suitable to highly sensitive optical temperature measurements is a critical challenge. In this work, BiTa7O19:Yb3+/Er3+ phosphor exhibits strong green emission and excellent green monochromaticity. The optimized BiTa7O19:Yb3+/Er3+ displays strong green UCL by 980 nm excitation, which can reach 70.29 times that of Y2O3:10%Yb3+/2%Er3+ and 6.23 times that of NaYF4:18%Yb3+/2%Er3+, respectively. The CIE chromaticity coordinates and calculated value indicate the excellent green monochromaticity. When Zn2+ ions were codoped, the green UCL intensity of BiTa7O19:40%Yb3+/20%Er3+/40%Zn2+ can be further enhanced by 2.62 times, and red UCL enhances 7.07 times, accordingly. This enhancement is attributed to the enhanced absorption of Yb3+ and Er3+ as well as improved energy transfer from Yb3+ to Er3+ due to lattice distortion caused by Zn2+ ion. The BiTa7O19:Yb3+/Er3+ and BiTa7O19:Yb3+/Er3+/Zn2+ phosphors both realize high sensitivity temperature sensing based on fluorescence intensity ratio of green UCL of Er3+. For the BiTa7O19:Yb3+/Er3+, the optimal relative sensitivities can reach up to 3.35% K−1 at 303 K. The measurement error obtained through thermal cycling remains consistently within ±1%, indicating good stability and repeatability. Collective findings verify that BiTa7O19:Yb3+/Er3+ phosphors are the favorable contenders for temperature sensors owned strong green UCL emission.

Noncontact optical temperature measurement has attracted considerable attention due to its crucial applications across various fields. However, the demand for highly sensitive optical thermometric materials remains pressing. This study introduces an ultrasensitive charge transfer band-based optical temperature sensing system utilizing Eu3+ monodoped MgNb2O6 phosphor, effectively circumventing the limitations associated with traditional thermally coupled energy levels. By utilizing the luminescence intensity ratio based on excitation and emission spectra, we introduced three measurement modes; the optical thermometer exhibited a maximum relative sensitivity of 4.24% K-1 (300 K) and an absolute sensitivity of 2.99% K-1 (570 K), surpassing the sensitivity of most optical thermometers of the same type. Furthermore, by employing the shift of charge transfer band peak position as a measurement parameter, we developed a novel optical thermometer with a sensitivity (Sw) of 0.064 nm·T-1. This material, exhibiting high brightness and high-purity red emission due to the efficient energy pathway provided by the ultraviolet absorption of the matrix, emerges as a promising candidate for LED applications. Additionally, ink and PDMS flexible films made of MgNb2O6:Eu3+ phosphor were prepared to illustrate potential applications in anticounterfeiting and encryption. All the studies demonstrate that the MgNb2O6:Eu3+ material is a promising candidate in the field of multimodal high-performance and multifunctional optical thermometers.

Multimode and highly sensitive optical temperature measurements are the key technology to improve the temperature monitor. In this work, doping-concentration-optimized BaNb2O6 materials show excellent temperature measurement performance, achieving multimode temperature measurement with self-calibration function upon a 980 nm laser diode pump. Four models of optically ultrasensitive temperature measurement are achieved in BaNb2O6: Yb3+/Er3+ and Yb3+/Ho3+ phosphors by making use of thermal coupling energy levels (Er3+: H-2(11/2)/S-4(3/2) and Ho3+: F-5(5)) and nonthermal coupling energy levels (Er3+: H-2(11/2)/S-4(3/2), F-4(9/2) and Ho3+: F-5(5), F-5(4)/S-5(2)). In the BaNb2O6: 7.0% Yb3+/5.0% Er3+ sample, we obtained maximum relative sensitivities (S-r) of Sr-g = 1.64% K-1 and Sr-Er = 1.48% K-1 at 298 K and maximum absolute sensitivities (S-a) of Sa-g = 0.33% K-1 and Sa-Er = 0.113% K-1 at 573 K corresponding to thermal coupling and nonthermal coupling energy levels, respectively. In the BaNb2O6: 7.0% Yb3+/0.5% Ho3+ sample, maximum S-r levels of Sr-r = 0.64% K-1 and Sr-Ho = 1.39% K-1 at 298 K and maximum S-a levels of Sa-r = 0.375% K-1 (298 K) and Sa-Ho = 1.25% K-1 (498 K) are obtained simultaneously. Throughout all the modes in the testing temperature range, excellent temperature resolution is exhibited, achieving an optimal value of 0.016 K. The four optical temperature sensors are validated to own excellent resolution, repeatability, and accuracy. All the studies demonstrate that BaNb2O6 is a promising candidate in the field of high-precision self-referencing multimode optical temperature measurements.

Yb3+-Er3+co-doped all inorganic cesium lead bromide perovskite nanocrystals were prepared by hot injec-tion method.The photoluminescence properties and crystal structure were characterized by transmission electron mi-croscopic,fluorescence spectrum and X-ray diffraction.The experimental results show that Yb3+-Er3+co-doped all in-organic perovskite nanocrystals emit bright green light(540 nm)and red light(646 nm)under the excitation of near-infrared light.In addition,it was found in the experimental process that the morphologies tuning of the Yb3+-Er3+co-doped perovskite bromide nanostructures i.e.quantum dots,nanotubes,nanorods,nanoflowers,nanobelts,nanosheets have been successfully achieved by controlling reaction temperature,the temperature injected by the pre-cursor and the proportion of the complexing agent and solvent.For Yb3+-Er3+co-doped perovskite nanocrystals with different morphology,the phenomenon of Yb3+sensitization Er3+luminescence was observed under the excitation of near-infrared light,which is due to the existence of Yb3+-Er3+energy transfer.Rare earth doping of perovskite materi-als can realize the up-conversion luminescence phenomenon under the excitation of near-infrared light,which is ben-eficial to the application of perovskite family materials in biomedical field.

A series of CaSc2O4:Er3+,Nd3+ nanocrystals were synthesized by the hydrothermal method. The lumines-cence properties of the CaSc2O4:Er3+,Nd3+ oxide crystals in the visible-light and near infrared (NIR) regions were in-vestigated in detail as the Nd3+ concentrations and excited wavelengths vary. Under 808 nm excitation, the lumines-cence intensity of Er3+ ions appears to be enhanced as the concentration of Nd3+ ions increase. The relative red intensi-ty also has the slight enhancement. Under 980 nm excitation, Nd3+ ions hardly absorb 980 nm photons, only the ab-sorption and emission of Er3+ ions are found. The relative red intensity has no change. Furthermore, only the emis-sion of Er3+ ion was observed in NIR spectrum, which is consist as the visible spectrum. The detailed study reveals the possible upconversion luminescence (UCL) mechanism involved in a novel CaSc2O4:Er3+,Nd3+ nanocrystals un-der 808 nm and 980 nm NIR excitation.

Temperature-sensing media based on the fluorescence intensity ratio (FIR) of upconversion materials that suffer from low sensitivity owing to the small energy gap still have a need for new compounds with strong upconversion luminescence (UCL). In this work, a series of MSc2O4:Er3+/Yb3+ (M = Mg, Ca, Sr, and Ba) nanocrystals were prepared by a hydrothermal method using NaOH alkaline solution. The structure, morphology, and UCL characteristics of materials were investigated, and the red UCL of the CaSc2O4:Er3+/Yb3+ sample was dramatically enhanced by a factor of ∼12, ∼23, and ∼2000 compared with SrSc2O4, MgSc2O4, and BaSc2O4 samples, respectively. By adjusting alkali ions (Li+, Na+, K+), the UCL intensities of CaSc2O4:Er3+/Yb3+ and SrSc2O4:Er3+/Yb3+ samples were further improved, especially in the presence of Li+ ions. Excellent temperature-sensing behaviors are realized for CaSc2O4:Er3+/Yb3+ and SrSc2O4:Er3+/Yb3+ samples in the presence of Li+ ions, in which the maximum absolute sensitivity SA values are about 0.0041 and 0.0036 K-1 at 600 K and the corresponding relative sensitivity SR values are expressed as 1197/T2 and 1129/T2 (the current optimal SR = 1289/T2), respectively. The intense UCL and excellent SA and SR values indicate that CaSc2O4:Er3+/Yb3+ and SrSc2O4:Er3+/Yb3+ materials are promising candidates for application in high-temperature sensors working under 980 nm excitation.

Monodisperse sub-10 nm Sc2O3: Yb, Er upconverting nanoparticles (UCNPs) were firstly synthesized via solvothermal method in three-neck round-bottom flask. The X-ray diffraction (XRD) shows that the prepared UCNPs possess cubic structure. The transmission electron microscopy (TEM) shows that sample has monodisperse spheroid morphology with high crystallinity. The average size of spheroid UCNPs could be controllable manipulated as small as 3 nm. Furthermore, the sample exhibits stronger red and green upconversion luminescence (UCL) than reported Sc2O3: Yb, Er nanostructure by biphasic solvothermal method. The Fourier transform infrared (FTIR) spectra and decay curve reveal that ultra-small Sc2O3: Yb, Er UCNPs exhibit the reduced surface groups and long decay time of Er3+ ions. The results indicate Sc2O3: Yb, Er UCNPs is a probable oxide material with small size and intense UCL for biological applications.

Monodisperse In2O3: Yb3+/Er3+ upconverting nanoparticles (UCNPs) were firstly synthesized via solvothermal method in three-neck round-bottom flask. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR) methods are used to characterize the prepared UCNPs. The size of monodisperse spheroid nanoparticles prepared can be controllable in 31 nm. The sample exhibits stronger upconversion luminescence (UCL) than reported In2O3: Yb3+/Er3+ UCNPs with similar size. Furthermore, the obtained In2O3 UCNPs, by coating the SiO2 protecting layer, display fine stability. Simultaneously, the UCL properties and possible energy transfer process of In2O3: Yb3+/Ho3+ and In2O3: Yb3+/Tm3+ NPs have also been investigated by the spectra distribution and power dependence. The results indicate Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ codoped In2O3 UCNPs is a probable oxide upconverting material with small size and intense UCL for biological applications.

通过水热法制备了碱金属离子（Li + 、Na + 、K + ）共掺的MgSc 2 O 4 ∶Er 3+ /Yb 3+ 纳米晶,获得类球状纳米晶的平均尺寸约为35 nm。通过改变碱金属离子的种类和数量,获得了增强上转换发光。发现K + 离子共掺MgSc 2 O 4 ∶Er 3+ /Yb 3+ 纳米晶发光强度最佳,并且随着K + 掺杂量的不断增加,纳米晶的发射强度逐渐增强,这是由于K + 离子引入了最大的晶体场不对称性。随后,通过调控Yb 3+ 和Er 3+ 的掺杂浓度,发现发光强度最强样品为K + 离子共掺MgSc 2 O 4 ∶1%Er 3+ /5%Yb 3+ 纳米晶。研究了在980 nm激光激发下,MgSc 2 O 4 纳米晶中Yb 3+ 与Er 3+ 离子之间的能量传递以及上转换发光机制。

The influence of organic additives (Cit-3Na, EDTA, CTAB et al.) on structure, crystallinity, morphology and upconversion properties for CaSc2O4 nanocrystals was investigated by hydrothermal synthesis. Via adding organic additives, we obtain rod-like and square-like CaSc2O4 nanocrystals. The sample choosing Cit-3Na as organic additive exhibits the best uniformity, monodispersity, narrowest size distribution and strongest red emission, which is enhanced by a factor of 2.5, in comparison with no adding the organic additives. Simultaneously, the upconversion luminescence properties and mechanism of Ln(3+) /Yb3+ (Ln(3+)= Er3+/Tm3+/Ho3+) doped CaSc2O4 nanocrystals were investigated by the spectra distribution and power dependence. The emitting color of CaSc2O4 nanocrystals can be tuned from blue to green and red. The results reveal that CaSc2O4: Er3+/Yb3+ nanocrystals is a perfect red emission material and CaSc2O4 is an ideal host for upconversion luminescence.

基于贵金属表面局域等离子体共振(LSPR)调控上转换荧光的研究绝大部分集中于纳米颗粒或纳米棒,即使同一复合结构对上转换荧光(UCL)也有或增强或猝灭的截然相反的报道,而对于进一步提高上转换荧光材料的效率和强度以满足更广泛的应用需求则越来越引起人们高度关注.本文通过构筑两种纳米金/上转换纳米晶复合结构,系统研究了各自的表面局域等离激元对上转换荧光的增强和猝灭效应,基于微结构表征及对稳态、瞬态荧光光谱的分析,阐述了波长依赖的上转换荧光增强和猝灭机理.结果显示超薄纳米金壳结构对Ho3+、Fe3+共掺杂纳米晶的绿光发射选择性地增强了25倍,源于激发光能量与LSPR能量匹配的激发增强机制,而在覆盖有超薄纳米金膜的上转换纳米晶复合结构中却观察到了金膜引起的Er上转换荧光猝灭,同时红绿比随金膜厚度增加而增大,来自于金膜对激发光的散射、金膜的LSPR吸收带与绿光发射能级耦合引起无辐射跃迁几率增加,绿光上转换荧光强度下降相对显著,UCL寿命变短.

The Sc2O3: Er3+, Yb3+ nanoparticles (NPs) with the size of about 19 nm were synthesized by a simple oleic acid-mediated hydrothermal (HT) process. X-ray diffraction (XRD), transmission electron microscopy (TEM), upconversion luminescence (UCL) spectra, and decay curves were used to characterize the resulting samples. The Sc2O3: Er3+, Yb3+ NPs made by HT method exhibit the stronger UCL, of which the red UCL are enhanced by a factor of 4, in comparison with those samples prepared by solvothermal (ST) method at the same optimized lanthanide ion concentrations. The UCL enhancement can be attributed to the reduced surface groups and longer lifetimes. Under 980 nm wavelength excitation, the decay curves of Er3+: (2H11/2, 4S3/2) → 4I15/2 and 4F9/2 → 4I15/2 emissions for Sc2O3: Er3+, Yb3+ NPs samples are both close to each other, resulting from the cross relaxation energy transfer from Er3+ to Yb3+, followed by an energy back transfer within the same Er3+-Yb3+ pair. Also, under the relatively low-power density, the slopes of the linear plots of log(I) vs. log(P) for red and green emissions are 2.5 and 2.1, implying the existence of three-photon processes. Our results indicate that Sc2O3: Er3+, Yb3+ NPs is an excellent material for achieving intense UCL with small size in the biological fields.

In this paper,introduces teaching principles of CNC practice,superficial analyzes every principle,It addresses that teacher should be good at correct choice and application of these principles to Guide teaching,in order to improve the quality of CNC practice.

本文阐述了大学物理演示实验的重要性,并结合我校的特点,总结如何上好物理演示实验。

A novel optic fiber curvature sensor is developed,in which the light loss brought by the tested structure distortion is measured out through a sensitive area.In the experiment,with cantilever beam,simply supported beam and standard cylinder,both the static and dynamic features,together with the directional character are tested through an amplifier.